Avionics News January 2012 - 66

DATA CONVERSION WITH COTS EQUIPMENT
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triplet of equally spaced MIL-STD-1553B messages received at 8.33 Hz. 2. The triplet of messages can switch to another triplet when the aircraft changes operational modes. To accommodate these input characteristics, the following features of the Lynx Converter unit could be used: • Time-stamp indicating the reception time of each incoming parameter. • Comparator function (used to compare time-stamps to determine the most current input value). • Conditional transmission of ARINC 429 labels (used to switch on and off the virtual data streams from the separate source addresses). In one actual case, these features enabled the quick modification of the Lynx Converter over a weekend to time-multiplex the data while rate changing the 25 Hz input rate to a 20 Hz output rate. The following time related functions are built into the Lynx Converter: • Time from unit power-up. • Time-stamp of received word. • Time since word last received. • Time from 1553B synchronize point to word last received. • Number of times word received (freshness counter). The following comparator related functions are built in to the Lynx Converter: • Compare input to constant (<, <=, =, >=, >, <>) and set a bit with the result. • Compare two input values (<, <=, =, >=, >, <>) and set a bit with the result. The conditional transmission capabilities built into the Lynx Converter are as follows: • ARINC 429 or 1553B transmissions can be conditional on the state of an input discrete or combinations of input discretes. • Bus controller operation can be conditional on the state of an input discrete or combinations of input discretes. • For redundant ARINC 429 input receivers, data output can be switched to the redundant input based on the state of an input or combinations of input discretes.

(BM = 1553B Bus Monitor; RT = 1553B Remote Terminal; BC = 1553B Bus Controller)

TYPICAL SYSTEM OVERVIEW

The PCU-100 Lynx Protocol Converter is being used in a number of applications and programs which are currently in different stages of development, ranging from system rig testing, to inflight testing, to in-production use. The following table lists some of the applications and projects using the Lynx Converter:
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The following is a representative example of the use of PCU100 Lynx Protocol Converter unit, where the unit is connected to an aircraft dual-redundant MIL-STD-1553B (“1553B”) databus to acquire aircraft data and generate outputs on four ARINC 429 (“ARINC”) databusses for a COTS avionics unit (see Figure 1). While the PCU-100 Lynx Protocol Converter can interface with a 1553B databus by acting as a bus monitor, remote terminal, or bus controller, or even combinations of these three interfaces, it is configured for this example as a bus monitor, which allows the capture of data from the 1553B bus without disturbing the existing bus operation or requiring any special commands from the existing bus controller. Once connected to a 1553B bus (via a transformer coupler), the Lynx Converter acting as a bus monitor observes all existing bus traffic and captures transmissions in parallel with the equipment normally on the bus. The COTS avionics expects specific data on four different ARINC inputs; the Lynx Converter meets this requirement by having four independent ARINC outputs, and is able to switch input data from either of two 1553B dual-redundant inputs or up to 12 ARINC inputs to any output.

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Avionics News January 2012

Table of Contents for the Digital Edition of Avionics News January 2012